NASA often interprets patterns in debris disks around new stars as a sign that the star system may have planets. A new study finds this might not always be the case.

When a star forms, a cloud of gas compresses until it finally ignites a fusion process. Sometimes, part of the cloud remains around the new star, forming a disk. The disk is composed of debris, ice, rocks and dust which collide with each other while they orbit the star. Sometimes, distinct lines or swirling patterns form in the disk, and this is usually indicative of the presence of a planet.

However, a new NASA study has found that this is not always the case. Under the right conditions, debris disks may create thin lines on their own, without the need of gravitational pull from a larger body. “When the mass of gas is roughly equal to the mass of dust, the two interact in a way that leads to clumping in the dust and the formation of patterns,” said lead researcher of the study, Wladimir Lyra, “In essence, the gas shepherds the dust into the kinds of structures we would expect to be see if a planet were present.”

The gas can be misleading due to the way NASA usually studies the disks. Dust, which is comparatively warm, can be detected rather easily in infrared scans, but the gas is much harder to detect. Thus, NASA usually ignores the gas when examining debris disks around new stars. “All we need to produce narrow rings and other structures in our models of debris disks is a bit of gas, too little for us to detect today in most actual systems,” said co-author Marc Kuchner.